there exist other (more flexible) ways of that check. if you have several countries and several currencies you can, for example, create the array which every member will look like:
and then you'll run two loops. the first loop finds 'country' looking over the first members of each member. if it doesn't match the loop skips the member (continue), but if it matches the first member the second loop which looks over the second member (the array of acceptable currencies) starts. if the second loop finds the given currency it breaks and submits the form.
anyway, you must understand that the better check is done at the server-side